Stuides are being conducted in three areas: 1) isolation of human glioma-associated cell surface antigens; 2) characterization of a substance, found in the serum of humans and mice that bear anaplastic tumors, that inhibits fundamental cell-cell interactions; 3) study of the capacity of normal cells, unrelated to the immune system, which have the capacity to inhibit tumor cell replication and biological activity. These studies employ mixed aggregates of normal and neoplastic human cells.